Color images are customarily obtained in the photographic art by reaction between an oxidation product of a silver halide developing agent and a dye-forming coupler. Pyrazolone couplers are useful for forming magenta dye images; however, such couplers have shortcomings with respect to color reproduction in that the unwanted absorption around 430 nm causes color turbidity. Bicyclic pyrazolo couplers, particularly pyrazolotriazole couplers, represent another class of couplers for this purpose. Examples of bicyclic pyrazolo couplers are described in, for example, U.S. Pat. Nos. 4,443,536; 1,247,493; 1,252,418; and 1,398,979; and 4,665,015; 4,514,490; 4,621,046, 4,540,654; 4,590,153; 4,822,730 and European Patents 177,765 and 119,860. One class of pyrazolotriazole couplers includes 1H-pyrazolo[3,2-c][1,2,4] triazole couplers and another includes 1H-pyrazolo[1,5-b][1,2,4] triazole couplers, such as described in European Patent 177765. While these couplers have a reduced level of unwanted absorption, the conversion of the coupler into an azomethine dye is slow and the attainable maximum density, contrast, and speed are reduced due to lower coupling efficiency. The aforementioned U.S. Pat. No. 4,822,730 discloses pyrazolotriazoles having a group expressed by the formula --(A) L-B where L represents --N(R) SO.sub.2 --, --SO.sub.2 N(R)--, or --N(R)SO.sub.2 N(R)--. The compounds exemplified contain a methyl or unbranched alkyl group at the 6-position rather that a fully substituted carbon. For example, the following compound is suggested: ##STR2## These couplers do not fully satisfy the needs for activity and color reproduction.
Bicyclic pyrazolo couplers containing a t-butyl group at the 6-position are described in U.S. Pat. No. 4,882,266. Such couplers suffer from the disadvantage of lower coupling reactivity manifested by lower contrast and Dmax as well as low speeds compared to the corresponding methyl substituted analogs.
Thus, while such magenta dye-forming couplers are useful in photographic silver halide materials and processes, many of such couplers do not have sufficient coupler reactivity. Moreover, the existing products are deficient with respect to obtainable speed, dye light stability, and color reproduction.
The problem with the existing couplers is that they do not provide a satisfactory combination of reactivity, light stability and color reproduction.